Communication apparatus, control method, and computer-readable recording medium

ABSTRACT

A communication apparatus includes a communication unit that communicates with an external apparatus via communication lines conforming to HDMI standard, a first detection unit that determines whether a first signal is detected indicating that the communication unit and the external apparatus are connected, a second detection unit that determines whether a second signal is detected indicating that the external apparatus is in a state where the external apparatus displays video data transmitted from the communication unit, and a control unit that controls the communication unit to transmit the video data to the external apparatus if the first signal and the second signal are detected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication apparatus thatcommunicates with an external apparatus, a control method, and acomputer-readable recording medium.

2. Description of the Related Art

At present, there are suggested communication systems which comply withthe High Definition Multimedia Interface (HDMI, registered trademark)standard (hereinafter referred to as the “HDMI systems”). The HDMIsystem includes a source apparatus that transmits video data and audiodata, and a sink apparatus that has a display apparatus to display videodata received from the source apparatus.

In an HDMI system, a user can cause the sink apparatus to display videodata reproduced from the source apparatus, and view desired video data.

Japanese Patent Application Laid-Open No. 2007-078980 discusses that, inthe above HDMI system, the source apparatus acquires Extended displayidentification data (EDID) from the sink apparatus, according to a HotPlug Detect (HPD) signal detected from the sink apparatus. Based on theacquired EDID, the source apparatus also transmits video data that thesink apparatus can output.

If video data received from the source apparatus is not compatible withthe EDID description, the sink apparatus does not output (or display)video data received from the source apparatus, even after the sinkapparatus receives video data from the source apparatus.

In such a case, even if the source apparatus continues to transmit videodata to the sink apparatus, the source apparatus merely consumes extrapower, as the sink apparatus does not display the video data transmittedfrom the source apparatus.

When an HPD signal is on, the sink apparatus outputs (displays) videodata compatible with the description of the EDID received from thesource apparatus, after transmitting the EDID to the source apparatus inresponse to an EDID request from the source apparatus.

Therefore, after the sink apparatus outputs (displays) video datareceived from the source apparatus, the source apparatus needs toacquire again the EDID of the sink apparatus so as to cause the sinkapparatus to output video data received from the source apparatus, evenif the source apparatus has already acquired the EDID from the sinkapparatus.

In such a case, after acquiring again the EDID of the sink apparatus,the source apparatus analyzes the acquired EDID. The source apparatusthen generates video data compatible with the description of the EDID ofthe sink apparatus, and transmits the video data to the sink apparatus.Therefore, there is a delay in outputting (displaying) the video datafrom the source apparatus by the sink apparatus.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided acommunication apparatus, comprising: a communication unit thatcommunicates with an external apparatus via a plurality of communicationlines conforming to High Definition Multimedia Interface (HDMI)standard; a first detection unit that determines whether a first signalis detected by the communication unit via a Hot Plug Detect (HPD) line,the first signal including a signal indicating that the communicationunit and the external apparatus are connected; a second detection unitthat determines whether a second signal is detected by the communicationunit via a Transition Minimized Differential Signaling (TMDS) line, thesecond signal including a signal indicating that the external apparatusis in a state where the external apparatus displays video data receivedfrom the communication unit; and a control unit that controls thecommunication unit to transmit the video data to the external apparatusvia the TMDS line if the first signal and the second signal aredetected.

Further features and aspects of the present invention will becomeapparent from the following description of exemplary embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the present invention and, together with the description,serve to explain the principles of the present invention.

FIG. 1 illustrates an example of a communication system according to afirst exemplary embodiment of the present invention.

FIG. 2 is a block diagram illustrating a communication apparatusaccording to the first exemplary embodiment of the present invention.

FIG. 3 is a flowchart illustrating image output control processingperformed by the communication apparatus according to the firstexemplary embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the presentinvention will be described in detail below with reference to theattached drawings.

A communication system according to a first exemplary embodiment of thepresent invention includes a communication apparatus 100, an externalapparatus 200, and a connection cable 300, as illustrated in FIG. 1. Thecommunication apparatus 100 and the external apparatus 200 are connectedvia the connection cable 300.

The communication apparatus 100 is an output apparatus that is capableof transmitting video data, audio data, and auxiliary data to theexternal apparatus 200 via the connection cable 300. The externalapparatus 200 is a display apparatus that displays video data receivedfrom the communication apparatus 100 on a display device, and outputsaudio data received from the communication apparatus 100 through aspeaker. Each of the communication apparatus 100 and the externalapparatus 200 is capable of bidirectionally transmitting various controlcommands via the connection cable 300.

In the first exemplary embodiment, the communication apparatus 100, theexternal apparatus 200, and the connection cable 300 conform to the HDMIstandard. Accordingly, the communication apparatus 100 is a sourceapparatus that functions as an HDMI source according to the HDMIstandard, and the external apparatus 200 is a sink apparatus thatfunctions as an HDMI sink according to the HDMI standard.

In the first exemplary embodiment, the communication apparatus 100 andthe external apparatus 200 conform to the Consumer Electronics Control(CEC) protocol set forth in the HDMI standard. The control commands tobe transmitted bidirectionally between the communication apparatus 100and the external apparatus 200 conform to the CEC protocol. Hereinafter,the control commands conform to the CEC protocol will be referred to asthe “CEC commands”.

In the first exemplary embodiment, a single-lens reflex camera(hereinafter referred to as a camera) is used as an example of thecommunication apparatus 100. The communication apparatus 100 is notlimited to a single-lens reflex camera, and a video output apparatussuch as a digital still camera, a digital video camera, a recorder, or adigital versatile disc (DVD) player may be used as the communicationapparatus 100, as long as the apparatus has the function of an HDMIsource apparatus.

In the first exemplary embodiment, a television receiver (hereinafterreferred to as “TV”) is used as an example of the external apparatus200. The external apparatus 200 isnot limited to a TV, and a displayapparatus such as a projector or a personal computer may be used as theexternal apparatus 200, as long as the apparatus has the function of anHDMI sink apparatus.

Hereinafter, the communication apparatus 100 will be referred to as the“camera 100”, the external apparatus 200 will be referred to as the “TV200”, and the connection cable 300 will be referred to as the “HDMIcable 300”.

Referring now to FIG. 2, the HDMI cable 300 is described.

The HDMI cable 300 includes a +5 V power line (not illustrated), a HotPlug Detect (HPD) line 301, and a Display Data Channel (DDC) line 302.The HDMI cable 300 further includes a Transition Minimized DifferentialSignaling (TMDS) line 303, and a CEC line 304.

The +5 V power line is a power supply line for supplying +5 V power fromthe camera 100 to the TV 200.

The HPD line 301 is a transmission line for transmitting an HPD signalof a high-voltage level (hereinafter referred to as the H-level) or alow-voltage level (hereinafter referred to as the L-level) from the TV200 to the camera 100.

If the camera 100 is supplying +5 V power to the TV 200 via the +5 Vpower line, the TV 200 determines whether the device information(capability information) about the TV 200 can be transmitted to thecamera 100.

The device information about the TV 200 is Extended Displayidentification data (EDID) or Enhanced EDID (E-EDID) of the TV 200. TheEDID and the E-EDID contain identification information about the TV 200,information about the display capability and audio capability of the TV200, as the device information about the TV 200. For example, the EDIDand the E-EDID contain information about the resolution, the scanningfrequency, the aspect ratio, and the color space supported by the TV200. The E-EDID is formed by enhancing the EDID, and contains moredevice information than the EDID does. For example, the E-EDID containsinformation about the formats of the video data and audio data supportedby the TV 200. Hereinafter, the EDID and the E-EDID will be bothreferred to as the “EDID”.

If the camera 100 is supplying +5 V power to the TV 200, and the TV 200can transmit the EDID to the camera 100, the TV 200 transmits an HPDsignal of the H-level to the camera 100 via the HPD line 301. Bytransmitting the HPD signal of the H-level to the camera 100, the TV 200can notify the camera 100 that the camera 100 can acquire the EDID.

In some cases, the TV 200 cannot transmit the EDID of the TV 200 to thecamera 100, although the camera 100 is supplying +5 V power to the TV200. This might be because the video settings, resolution settings, andaudio settings in the EDID of the TV 200 are changed, and the TV 200rewrites the information contained in the EDID. In such a case, the TV200 transmits an HPD signal of the L-level to the camera 100 via the HPDline 301 until completing the rewriting of the EDID. After completingthe rewriting of the EDID, the TV 200 transmits an HPD signal of theH-level to the camera 100 via the HPD line 301. If the camera 100 is notsupplying +5 V power to the TV 200, the TV 200 also transmits an HPDsignal of the L-level to the camera 100.

The DDC line 302 is a transmission line for transmitting the EDID of theTV 200 from the TV 200 to the camera 100. Receiving the EDID of the TV200, the camera 100 refers to the EDID of the TV 200, to automaticallyrecognize the display capability, the audio capability, and the like ofthe TV 200. Further, a CPU 101 can automatically recognize the videoformat and the audio format compatible with the display capability andthe audio capability of the TV 200. By changing the settings of thecamera 100 to the settings compatible with the TV 200, the camera 100can change the video data and the audio data transmitted from the camera100 to the TV 200 to video data and audio data compatible with thecapability of the TV 200.

The TMDS line 303 is a transmission line for transmitting video data,audio data, and auxiliary data from the camera 100 to the TV 200. TheTMDS line 303 includes a TMDS channel 0, a TMDS channel 1, a TMDSchannel 2, and a TMDS clock channel.

The CEC line 304 is a transmission line for transmitting various CECcommands bidirectionally between the camera 100 and the TV 200. The TV200 can control the camera 100 by transmitting CEC commands forcontrolling the camera 100 to the camera 100 via the CEC line 304.

Referring now to FIG. 2, an example configuration of the camera 100 isdescribed.

As illustrated in FIG. 2, the camera 100 includes the central processingunit (CPU) 101, a memory 102, a communication unit 103, an image captureunit 104, a recording unit 105, a display unit 106, an operation unit107, and a power supply unit 108. The following is a description of thecamera 100.

The CPU 101 controls the entire operations of the camera 100, accordingto a computer program stored in the memory 102. The CPU 101 can alsocontrol the entire operations of the camera 100, using the EDID of theTV 200. By analyzing data supplied from each component of the camera100, the CPU 101 controls the entire camera 100. The CPU 101 alsoperforms a control operation so that the power supply unit 108 suppliespower to each component or stops supplying power.

The memory 102 functions as a work area for the CPU 101. The informationstored in the memory 102 includes the EDID of the TV 200 and the resultsof an analysis performed on the EDID of the TV 200 by the CPU 101. Also,the flag settings for the operations of the respective components andthe results of operations and analyses performed by the CPU 101 arerecorded in the memory 102. The work area for the CPU 101 is not limitedto the memory 102, and may be an external recording apparatus such as ahard disk device.

The communication unit 103 includes a connection terminal for connectingthe HDMI cable 300. The communication unit 103 acquires the EDID of theTV 200 via the connection terminal, and transmits and receives CECcommands. The communication unit 103 also transmits video data, audiodata, and auxiliary data. The communication unit 103 further generates a5 V voltage from the power supplied from the power supply unit 108, andsupplies the 5 V voltage to the TV 200 via the +5 V power line. Thecommunication unit 103 includes a first connection detection unit 103 a,a second connection detection unit 103 b, a capability informationacquisition unit 103 c, and a packet processing unit 103 d.

The first connection detection unit 103 a can receive an HPD signal ofthe H-level or an HPD signal of the L-level transmitted from the TV 200via the HPD line 301. When the CPU 101 issues a request for the receivedHPD signal, the first connection detection unit 103 a supplies the HPDsignal to the CPU 101.

To detect the existence of the TV 200, the second connection detectionunit 103 b can determine, via the TMDS line 303, whether the TMDS line303 is connected to a terminal resistor on the side of the TV 200. Anexample of information to be used to determine whether the TMDS line 303is connected to the terminal resistor on the side of the TV 200 isinformation called “Receiver Sense (hereinafter referred to as the “RXsense”). The RX sense includes Rx sense of the H-level indicating thatthe TMDS line 303 is connected to the terminal resistor on the side ofthe TV 200, and RX sense of the L-level indicating that the TMDS line303 is not connected to the terminal resistor on the side of the TV 200.When the TMDS line 303 is connected to the terminal resistor on the sideof the TV 200, the second connection detection unit 103 b detects the RXsense of the H-level. When the TMDS line 303 is not connected to theterminal resistor on the side of the TV 200, the second connectiondetection unit 103 b detects the RX sense of the L-level.

When the TMDS line 303 is connected to the terminal resistor on the sideof the TV 200, the TV 200 is in an output state. The output state is apower ON state, and is a state in which video data received from thecamera 100 via the TMDS line 303 is selected as the video data to bedisplayed by the TV 200. Accordingly, when the second connectiondetection unit 103 b detects the RX sense of the H-level, the CPU 101determines that the TV 200 is in the video image output state.

When the TMDS line 303 is not connected to the terminal resistor on theside of the TV 200, the TV 200 is in a non-output state. The non-outputstate is a state that does not satisfy at least one of the followingstates: where the TV 200 is in the power ON state, and where video datareceived from the camera 100 via the TMDS line 303 is selected as thevideo data to be displayed by the TV 200. Accordingly, when the secondconnection detection unit 103 b detects the RX sense of the L-level, theCPU 101 determines that the TV 200 is in the non-output state.

In response to a request from the CPU 101, the second connectiondetection unit 103 b supplies the detected RX sense to the CPU 101.According to the RX sense supplied from the second connection detectionunit 103 b, the CPU 101 determines whether the TV 200 can display thevideo data that is output from the camera 100, or whether the state ofthe TV 200 is the output state.

The capability information acquisition unit 103 c can acquire the EDIDfrom the TV 200 via the DDC line 302. When the HPD signal supplied fromthe first connection detection unit 103 a to the CPU 101 is the H-level,the capability information acquisition unit 103 c can acquire the EDIDof the TV 200 from the TV 200 via the DDC line 302. When the HPD signalsupplied from the first connection detection unit 103 a to the CPU 101is the L-level, the capability information acquisition unit 103 c cannotacquire the EDID from the TV 200 via the DDC line 302. When acquiringthe EDID, the capability information acquisition unit 103 c supplies theacquired EDID to the CPU 101. The CPU 101 analyzes the supplied EDID,and records the supplied EDID and the results of the EDID analysis inthe memory 102.

The packet processing unit 103 d can transmit video data, audio data,and auxiliary data to the TV 200 via the TMDS line 303. When theoperation mode of the camera 100 is an image capture mode, the packetprocessing unit 103 d can transmit video data generated by the imagecapture unit 104 and audio data generated by a microphone unit (notillustrated) to the TV 200 via the TMDS line 303. In this case,auxiliary data generated by the CPU 101 is also transmitted, togetherwith the video data and the audio data, to the TV 200 via the TMDS line303. When the operation mode of the camera 100 is a playback mode, thepacket processing unit 103 d can transmit video data and audio datareproduced from a recording medium 105 a by the recording unit 105, andauxiliary data generated by the CPU 101, to the TV 200 via the TMDS line303. Alternatively, the packet processing unit 103 d may transmit videodata and audio data separately from each other.

Also, the necessary power for transmitting video data, audio data, andauxiliary data to the TV 200 is supplied to the packet processing unit103 d from the power supply unit 108 under the control of the CPU 101.When the HDMI cable 300 is inserted to a connection terminal of thecamera 100 and a connection terminal of the TV 200, the CPU 101 controlsthe power supply unit 108 to supply power to the packet processing unit103 d, to cause the packet processing unit 103 d to change from a lowpower consumption state to a normal state. The normal state in thepacket processing unit 103 d is a state where the power supply unit 108is supplying the packet processing unit 103 d with the power necessaryfor the packet processing unit 103 d to transmit video data, audio data,and auxiliary data to the TV 200. The low power consumption state in thepacket processing unit 103 d is a state where the power supply unit 108does not supply the packet processing unit 103 d with the powernecessary for the packet processing unit 103 d to transmit video data,audio data, and auxiliary data to the TV 200.

After changing to the normal state, the packet processing unit 103 d isenabled, and becomes able to transmit video data, audio data, andauxiliary data to the TV 200 via the TMDS line 303. The CPU 101 controlsthe power supply unit 108 to stop supplying power to the packetprocessing unit 103 d, to cause the packet processing unit 103 d tochange from the normal state to the low power consumption state. Whenthe HDMI cable 300 is disconnected from the connection terminal of thecamera 100 and the connection terminal of the TV 200, the CPU 101 alsocontrols the power supply unit 108 to cause the packet processing unit103 d to change from the normal state to the low power consumptionstate. In this case, the packet processing unit 103 d is disabled, andbecomes unable to transmit video data, audio data, and auxiliary data tothe TV 200 via the TMDS line 303.

When the operation mode of the camera 100 is an image capture mode, theimage capture unit 104 captures an image of an object, and generatesvideo data from an optical image of the object. The video data generatedby the image capture unit 104 may be either a moving image or a stillimage. The video data generated by the image capture unit 104 issupplied from the image capture unit 104 to the packet processing unit103 d, the recording unit 105, and the display unit 106. If the EDID hasbeen successfully received from the TV 200, the image capture unit 104converts the video data to be supplied from the image capture unit 104to the packet processing unit 103 d, into video data compatible with thedisplay capability of the TV 200. The video data supplied from the imagecapture unit 104 to the packet processing unit 103 d is transmitted tothe TV 200 via the TMDS line 303. The video data supplied from the imagecapture unit 104 to the recording unit 105 is recorded in the recordingmedium 105 a. The display unit 106 displays the video data supplied fromthe image capture unit 104 to the display unit 106.

When the image capture unit 104 generates video data, the microphoneunit (not illustrated) generates audio data. The audio data generated bythe microphone unit is supplied from the microphone unit to the packetprocessing unit 103 d, the recording unit 105, and a speaker unit (notillustrated). If the EDID has been successfully received from the TV200, the microphone unit converts the audio data to be supplied from themicrophone unit to the packet processing unit 103 d, into audio datacompatible with the audio capability of the TV 200. The audio datasupplied from the microphone unit to the packet processing unit 103 istransmitted to the TV 200 via the TMDS line 303. The audio data suppliedfrom the microphone unit to the recording unit 105 is recorded in therecording medium 105 a. The speaker unit (not illustrated) outputs theaudio data supplied from the microphone unit to the display unit 106.

When the operation mode of the camera 100 is a playback mode, the imagecapture unit 104 stops capturing an image of an object, and stopsgenerating video data from an optical image of the object.

When the operation mode of the camera 100 is the image capture mode, therecording unit 105 can record the video data generated by the imagecapture unit 104 and the audio data generated by the microphone unit inthe recording medium 105 a. The CPU 101 controls the recording of thevideo data and the audio data generated by the image capture unit 104and the microphone unit in the recording medium 105 a, according to aninstruction that is input from a user via the operation unit 107.

When the operation mode of the camera 100 is the playback mode, therecording unit 105 can reproduce the video data and audio data selectedby a user from the recording medium 105 a. The CPU 101 controls theselection of the video data and the audio data reproduced from therecording medium 105 a, according to an instruction that is input from auser via the operation unit 107.

The video data reproduced from the recording medium 105 a by therecording unit 105 is supplied from the recording unit 105 to the packetprocessing unit 103 d and the display unit 106. If the capabilityinformation acquisition unit 103 c has successfully received the EDIDfrom the TV 200, the recording unit 105 converts the video data to besupplied from the recording unit 105 to the packet processing unit 103d, into video data compatible with the display capability of the TV 200according to the EDID. The video data supplied from the recording unit105 to the packet processing unit 103 d is transmitted to the TV 200 viathe TMDS line 303. The display unit 106 displays the video data suppliedfrom the recording unit 105 to the display unit 106. The audio datareproduced from the recording medium 105 a by the recording unit 105 issupplied from the recording unit 105 to the packet processing unit 103 dand the speaker unit (not illustrated). If the capability informationacquisition unit 103 c has successfully received the EDID from the TV200, the recording unit 105 converts the audio data to be supplied fromthe recording unit 105 to the packet processing unit 103 d, into audiodata compatible with the audio capability of the TV 200 according to theEDID. The audio data supplied from the recording unit 105 to the packetprocessing unit 103 d is transmitted to the TV 200 via the TMDS line303. The speaker unit outputs the audio data supplied from the recordingunit 105 to the speaker unit.

The recording medium 105 a is a recording medium such as a memory cardor a hard disk device. The recording medium 105 a may be either arecording medium provided in the camera 100 or a recording mediumdetachable from the camera 100.

The display unit 106 includes a display device such as a liquid crystaldisplay. When the operation mode of the camera 100 is the image capturemode, the display unit 106 displays the video data generated by theimage capture unit 104. When the operation mode of the camera 100 is theplayback mode, the display unit 106 displays the video data reproducedfrom the recording medium 105 a by the recording unit 105.

The operation unit 107 provides a user interface for operating thecamera 100. The operation unit 107 includes buttons for operating thecamera 100. The buttons in the operation unit 107 include switches andtouch panels. The CPU 101 can control the camera 100, according to aninstruction that is input from a user via the operation unit 107.

The power supply unit 108 supplies necessary power to a battery or an ACpower supply detachable from the camera 100, and to the respectivecomponents of the camera 100. A power OFF state is a state where thepower supply unit 108 has partially or entirely stopped supplying powerto the camera 100. A power ON state is a state where the power supplyunit 108 is supplying power partially or entirely to the camera 100.

Referring now to FIG. 2, an example configuration of the TV 200 isdescribed.

The TV 200 includes a CPU 201, a tuner unit 202, a communication unit203, a display unit 204, an operation unit 205, a memory 206, and apower supply unit 207, as illustrated in FIG. 2.

The CPU 201 controls the operation of the entire TV 200, according to acomputer program stored in the memory 206. The CPU 201 also controls thepower supply unit 207 to supply power to the respective components orstop supplying power.

The tuner unit 202 receives television broadcasts on a televisionchannel selected by a user. A television channel is selected with theuse of the operation unit 205 or a remote controller (not illustrated).The CPU 201 controls the tuner unit 202, according to an instructionthat is input from a user via the operation unit 205. Accordingly, thetuner unit 202 can receive the television broadcasts on the televisionchannel selected by a user using the remote controller (not illustrated)or the operation unit 205. The display unit 204 displays the video datacontained in the television broadcasts received by the tuner unit 202.The speaker unit (not illustrated) outputs the audio data contained inthe television broadcasts received by the tuner unit 202. The auxiliarydata contained in the television broadcasts received by the tuner unit202 is supplied to the CPU 201. The CPU 201 can control the TV 200,according to the auxiliary data received from the camera 100.

The communication unit 203 includes connection terminals that connect tothe HDMI cable 300. The communication unit 203 can receive, via the TMDSline 303, video data, audio data, and auxiliary data transmitted fromthe camera 100. The display unit 204 displays the video data receivedfrom the camera 100. The speaker unit (not illustrated) outputs theaudio data received from the camera 100. The auxiliary data receivedfrom the camera 100 is supplied to the CPU 201. The CPU 201 can controlthe TV 200, according to the auxiliary data received from the camera100.

The number of connection terminals included in the communication unit203 varies among TVs 200. Each TV 200 can connect to source apparatusesexcluding the camera 100 via the same number of HDMI cables as thenumber of connection terminals. Accordingly, the TV 200 can receivevideo data, audio data, and auxiliary data transmitted from sourceapparatuses that are connected to the TV 200 and exclude the camera 100.In this case, the display unit 204 displays the video data received fromthe source apparatuses excluding the camera 100, the speaker unit (notillustrated) outputs the audio data, and the auxiliary data is suppliedto the CPU 201. The communication unit 203 can receive CEC commandstransmitted from the camera 100 via the CEC line 304, and transmits CECcommands generated by the CPU 201 to the camera 100.

The communication unit 203 determines whether the camera 100 issupplying +5 V to the TV 200 via the +5 V power line, and, based on thedetermination result, transmits an HPD signal of the H-level or an HPDsignal of the L-level to the camera 100 via the HPD line 301. When thecommunication unit 203 is not receiving the +5 V power from the camera100 via the +5 V power line, the CPU 101 controls the communication unit203 to transmit an HPD signal of the L-level to the camera 100 via theHPD line 301.

When the communication unit 203 is receiving the +5 V power from thecamera 100 via the +5 V power line, the CPU 201 determines whether theEDID of the TV 200 stored in the memory 206 can be transmitted to thecamera 100 via the DDC line 302. If the information contained in theEDID stored in the memory 206 has not been changed, or if rewriting ofthe EDID has been completed, the CPU 201 determines that the EDID of theTV 200 can be transmitted to the camera 100 via the DDC line 302. Inthis case, the CPU 201 controls the communication unit 203 to transmitan HPD signal of the H-level to the camera 100 via the HPD line 301. Ifthe information contained in the EDID has been rewritten by changing thesettings for the TV 200, the CPU 201 determines that the EDID of the TV200 cannot be transmitted to the camera 100 via the DDC line 302. Inthis case, the CPU 201 also controls the communication unit 203 totransmit an HPD signal of the L-level to the camera 100 via the HPD line301.

The communication unit 203 can also transmit the EDID of the TV 200 tothe camera 100 via the DDC line 302.

The display unit 204 includes a display device such as a liquid crystaldisplay. The display unit 204 can display video data that is suppliedfrom at least one of the tuner unit 202 and the communication unit 203.When the communication unit 203 supplies video data received from thecamera 100, the display unit 204 displays the video data received fromthe camera 100.

The operation unit 205 provides a user interface for operating the TV200. The operation unit 205 includes buttons for operating the TV 200.The buttons of the operation unit 205 are formed with stitches, touchpanels, and the like. The CPU 201 can control the TV 200, according toan instruction that is input from a user via the operation unit 205. Theoperation unit 205 includes a power button, channel selection buttons,an external input button, and the like for operating the TV 200.

The power button is a button for instructing the CPU 201 to change theTV 200 from the power ON state or the power OFF state. The power NOstate is a state where the CPU 201 controls the power supply unit 207 tosupply the necessary power to all the components of the TV 200. Thepower OFF state is a state where the CPU 201 controls the power supplyunit 207 to stop supplying power to part of the TV 200 or to all thecomponents of the TV 200.

The channel selection buttons are buttons for selecting a televisionchannel the tuner unit 202 is to receive.

The external input button is a button for selecting the video datacontained in television broadcasts received by the tuner unit 202 or thevideo data received by the connected camera 100 via the HDMI cable 300,and causing the display unit 204 to display the selected video data.

The power supply unit 207 supplies the necessary power to the respectivecomponents of the TV 200 from an AC power supply or the like.

Referring now to FIG. 3, a video output control process to be performedby the camera 100 according to the first exemplary embodiment isdescribed.

FIG. 3 is a flowchart illustrating an example of the video outputcontrol process performed by the camera 100 according to the firstexemplary embodiment. The video output control process is performedwhere the HDMI cable 300 is inserted to a connection terminal of thecamera 100 and a connection terminal of the TV 200. The video outputcontrol process is performed while the camera 100 is supplying a 5 Vvoltage to the TV 200 via the +5 V power line. The CPU 101 executes acomputer program stored in the memory 102, to control the video outputcontrol process. Alternatively, the computer program for causing thecamera 100 to perform the procedures of the video output control processillustrated in FIG. 3 may be realized by utilizing the operating system(OS) operating on the computer.

When the HDMI cable 300 is inserted to a connection terminal of thecamera 100 and a connection terminal of the TV 200, the CPU 101 requeststhe first connection detection unit 103 a to supply an HPD signal.Depending on whether the HPD signal supplied from the first connectiondetection unit 103 is an HPD signal of the H-level or an HPD signal ofthe L-level, the CPU 101 determines whether the EDID of the TV 200 canbe acquired from the TV 200 via the DDC line 302.

When the first connection detection unit 103 a supplies an HPD signal ofthe H level, the CPU 101 determines whether the EDID can be acquired viathe DDC line 302 (YES in step S301). The process proceeds from step S301to step S302. When the first connection detection unit 103 a supplies anHPD signal of the L-level, the CPU 101 determines that the EDID cannotbe acquired via the DDC line 302 (NO in step S301). The process proceedsfrom step S301 to step S306. If the first connection detection unit 103a supplies an HPD signal of the L-level, the TV 200 might have rewrittenthe information contained in the EDID of the TV 200. Also, when the HDMIcable 300 is disconnected from the connection terminal of the camera 100and the connection terminal of the TV 200, the first connectiondetection unit 103 a supplies an HPD signal of the L-level.

When an HPD signal of the H-level is supplied (YES in step S301), theCPU 101 needs to determine whether the camera 100 has acquired the EDIDof the TV 200 from the TV 200 via the DDC line 302. Therefore, in stepS302, the CPU 101 determines whether the EDID of the TV 200 is recordedin the memory 102.

If the CPU 101 determines that the EDID acquired from the TV 200 via theDDC line 302 is already recorded in the memory 102 (YES in step S302),the process proceeds from step S302 to step S304.

If the CPU 101 determines that the EDID of the TV 200 is not recorded inthe memory 102 (NO in step S302), the process proceeds from step S302 tostep S303.

If the CPU 101 determines that the EDID of the TV 200 is not recorded inthe memory 102 (NO in step S302), the camera 100 cannot transmit videodata that is compatible with the display capability of the TV 200 beforeacquiring the EDID of the TV 200. Therefore, in step S303, thecapability information acquisition unit 103 c acquires the EDID from theTV 200 via the DDC line 302, and supplies the acquired EDID of the TV200 to the CPU 101. The CPU 101 analyzes the EDID supplied from thecapability information acquisition unit 103 c, and records the resultsof the EDID analysis and the EDID in the memory 102. After the CPU 101records the results of the EDID analysis and the EDID in the memory 102,the process proceeds from step S303 to step S304.

If the EDID acquired from the TV 200 is already recorded in the memory102 (YES in step S302), the CPU 101 can transmit video data to the TV200, according to the EDID in the memory 102.

When the capability information acquisition unit 103 c acquires the EDIDfrom the TV 200 in step S303, the CPU 101 can transmit video data to theTV 200, according to the EDID acquired in step S303.

In such a case, if the TV 200 is not in the output state, the video datareceived from the camera 100 cannot be displayed, even though the camera100 has transmitted the video data to the TV 200 according to the EDID.Asa result, the user not only is unable to view the video datatransmitted from the camera 100 on the TV 200, but also consumes extrapower from the camera 100. Therefore, the CPU 101 needs to determinewhether the TV 200 is in the output state, before video data convertedinto a video format included in the EDID is transmitted to the TV 200.

In step S304, the CPU 101 requests the second connection detection unit103 b to supply the RX sense of the TV 200, and, based on the RX sensesupplied from the second connection detection unit 103 b, the CPU 101determines whether the TV 200 is in the output state. The CPU 101 storesthe RX sense supplied from the second connection detection unit 103 binto the memory 102. When the second connection detection unit 103 bsupplies the RX sense of the H-level, the CPU 101 determines that the TV200 is in the output state (YES in step S304). The process proceeds fromstep S304 to step S305. When the second connection detection unit 103 bsupplies the RX sense of the L-level, the CPU 101 determines that the TV200 is in the non-output state. When the CPU 101 determines that the TV200 is in the non-output state (NO in step S304), the process proceedsfrom step S304 to step S307.

If the camera 100 transmits video data to the TV 200 while the TV 200 isin the output state (YES in step S304), the TV 200 can display the videodata received from the camera 100. In step S305, the CPU 101 performs avideo output process. The video output process includes formatconversion process and data transmission process of transmitting videodata to the TV 200. The format conversion process is a process ofconverting the format of the video data to be supplied to the packetprocessing unit 103 d to transmit the video data to the TV 200, into avideo format that can be displayed on the TV 200, according to theresults of the EDID analysis stored in the memory 102. Further, in theformat conversion process, the format of the audio data to betransmitted to the TV 200 is converted to an audio format that can beoutput as sound from the TV 200, according to the results of the EDIDanalysis stored in the memory 102.

If the EDID acquired from the TV 200 is already recorded in the memory102 (YES in step S302), the CPU 101 converts the video data to betransmitted to the TV 200, into a video format included in the EDID inthe memory 102.

When the capability information acquisition unit 103 c acquires the EDIDfrom the TV 200 in step S303, the CPU 101 converts the video data to betransmitted to the TV 200, into a video format included in the EDIDacquired in step S303.

When the format conversion process has already been performed, theformat conversion process may be skipped.

The data transmission process is performed by the packet processing unit103 d to transmit video data and audio data converted into predeterminedformats in the format conversion processing to the TV 200 via the TMDSline 303. If the packet processing unit 103 d is in the low powerconsumption state, the data transmission process may include process ofcontrolling the power supply unit 108 to return the packet processingunit 103 d from the low power consumption state to the normal state.After the CPU 101 performs the process to transmit video data to the TV200, the process returns from step S305 to step S301.

If an HPD signal of the L-level is supplied (NO in step S301), the CPU101 cannot acquire the EDID from the TV 200 via the DDC line 302 untilan HPD signal of the H-level is supplied. When the TV 200 supplies anHPD signal of the L-level to the camera 100, there is a possibility thatthe TV 200 has rewritten the information contained in the EDID of the TV200. When the HPD signal of the H-level is again supplied after the HPDsignal of the L-level is supplied, there is a possibility that theapparatus supplying the HPD signal of the H-level is a sink apparatusother than the TV 200. Here, the EDID might be transmitted from the newsink apparatus. In such a case, if the EDID and the results of the EDIDanalysis performed by the CPU 101 are recorded in the memory 102, thereis a possibility that those pieces of information are not the correctEDID of the sink apparatus connected via an HDMI cable and the correctresults of an analysis performed on the EDID. Therefore, in step S306,the CPU 101 discards the EDID and the results of the EDID analysisrecorded in the memory 102.

After the CPU 101 discards the EDID and the results of the EDID analysisrecorded in the memory 102, the process proceeds from step S306 to stepS307. Although the CPU 101 discards the EDID and the results of the EDIDanalysis recorded in the memory 102, the process is not limited to thatin step S306. For example, an invalid flag indicating that the EDID andthe results of the EDID analysis recorded in the memory 102 are invalidmay be set, and, at the time of transmission of video data, the CPU 101may perform a control operation not to use the EDID and the results ofthe EDID analysis for which the invalid flag is set.

If the TV 200 is in the non-output state (NO in step S304), the TV 200cannot display video data transmitted from the camera 100 until the userchanges the TV 200 to the output state. In such a case, the TV 200cannot display video data received from the camera 100, even if the CPU101 controls the packet processing unit 103 d to transmit the video datato the TV 200. As a result, extra power is consumed in the packetprocessing unit 103 d.

If the EDID and the results of the EDID analysis are discarded in stepS306, it is not possible to acquire the EDID from the TV 200 via the DDCline 302 until an HPD signal of the H-level is supplied to the CPU 101.Therefore, video data is not transmitted to the TV 200 via the TMDS line303, since the CPU 101 cannot convert the video data to be supplied tothe packet processing unit 103 d into a video format that can bedisplayed on the TV 200. Even if the CPU 101 continues to control thepower supply unit 108 to supply the packet processing unit 103 d withthe necessary power to transmit video data, video data is nottransmitted to the TV 200. As a result, the packet processing unit 103 dcontinues to consume extra power.

Therefore, in step S307, the CPU 101 stops the packet processing unit103 d from transmitting video data, and performs a process of changingthe packet processing unit 103 d into the low power consumption state.The processing of changing the packet processing unit 103 d into the lowpower consumption state is a process of stopping supplying power fromthe power supply unit 108 to the packet processing unit 103 d. When thepacket processing unit 103 d is in the low power consumption state, thefirst connection detection unit 103 a, the second connection detectionunit 103 b, and the capability information acquisition unit 103 c are inthe normal state. Therefore, the first connection detection unit 103 adetects HPD signals, the second connection detection unit 103 b detectsthe RX sense, and the capability information acquisition unit 103 c canacquire the EDID when the first connection detection unit 103 a detectsan HPD signal of the H-level. After the CPU 101 performs the process tochange the packet processing unit 103 d into the low power consumptionstate, the process returns from step S307 to step S301.

As described above, in the first exemplary embodiment, when the firstconnection detection unit 103 a supplies an HPD signal of the L-level(NO in step S301), the camera 100 stops supplying power to the packetprocessing unit 103 d. Since the camera 100 cannot transmit video dataconverted into a video format to be displayed on the TV 200 to the TV200, a control operation is successfully performed not to transmit videodata. In such a case, the camera 100 performs the control operation tostop the packet processing unit 103 d from transmitting video data.Accordingly, the process executed by the camera 100 to transmit videodata to an external apparatus is reduced, and the power consumption forthe packet processing unit 103 d can be reduced. In this manner, thepower consumption in the entire camera 100 can be reduced.

When the TV 200 is determined to be in the non-output state based on theRX sense of the TV 200 supplied from the second connection detectionunit 103 b (NO in step S304), the camera 100 stops supplying power tothe packet processing unit 103 d. By doing so, the camera 100 canperform a control operation so that the TV 200 in the power OFF state orthe TV 200 outputting video data and audio data supplied from anotherapparatus stops transmitting video data. Accordingly, the powerconsumption in the entire camera 100 can be reduced.

When the EDID acquired from the TV 200 is recorded in the memory 102(YES in step S302), the camera 100 does not acquire the EDID again, anddoes not analyze the acquired EDID. With this arrangement, the camera100 does not need to perform the EDID acquisition process. Accordingly,when the TV 200 is in the output state (YES in step S304), for example,the time required for the camera 100 to transmit video data to the TV200 can be shortened.

When the first connection detection unit 103 a supplies an HPD signal ofthe H-level (YES in step S301), the camera 100 keeps storing the EDIDacquired once from the TV 200, even if the TV 200 is in the non-outputstate. Accordingly, when the TV 200 is changed into to the output state(YES in step S304), it is unnecessary to reacquire the EDID from the TV200, and the time required for the camera 100 to transmit video data tothe TV 200 can be shortened.

As described above, in the camera 100 according to the first exemplaryembodiment, video data and audio data transmission by the camera 100 canbe controlled, depending on whether the TV camera 200 is in the outputstate where video data transmitted from the camera 100 to the TV 200 canbe displayed. Further, once the camera 100 acquires the EDID from the TV200, the camera 100 according to the first exemplary embodiment storesthe acquired EDID, unless the EDID is rewritten or the HDMI cable 300 isdisconnected. Accordingly, it is not necessary to reacquire the EDIDfrom the TV 200, and video data can be transmitted to the TV 200.

With the above arrangement, the power consumption in the camera 100 canbe reduced according to the state of the TV 200, and the powerconsumption in the entire camera 100 can be reduced. Also, the timerequired for the camera 100 to transmit video data can be shortened.

The camera 100 and the TV 200 according to the first exemplaryembodiment may be apparatuses not conforming to the CEC protocol.

In the first exemplary embodiment, a check is made to determine whetherthe terminal resistor on the side of the TV 200 is connected to the TMDSline 303, based on the RX sense. However, based on information otherthan the RX sense, a check may be made to determine whether the terminalresistor on the side of the TV 200 is connected to the TMDS line 303.

In the first exemplary embodiment, the communication apparatus 100 hasbeen described as a source apparatus that conforms to the HDMI standard,and the external apparatus 200 has been described as a sink apparatusthat conforms to the HDMI standard. However, they are not limited to theabove apparatuses, as long as the video output control process accordingto the first exemplary embodiment can be performed.

The communication apparatus according to an exemplary embodiment of thepresent invention is not limited to the communication apparatus 100according to the first exemplary embodiment, and may be realized by asystem including more than one apparatuses, for example.

In the first exemplary embodiment, a computer program for causing thecamera 100 to perform the procedures in the flowchart illustrating theabove described video output control process is read from a computerreadable recording medium, and is executed by a computer. The computerreadable recording medium may be a hard disk device, an optical disk, acompact disc read only memory (CD-ROM), a CD recordable (CD-R), a memorycard, a ROM, or the like. Also, a computer program according to thepresent invention may be supplied from an external apparatus to acomputer via a communication interface, and may be executed by thecomputer.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the present inventionis not limited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, and equivalent structures and functions.

This application claims priority from Japanese Patent Application No.2009-188602 filed Aug. 17, 2009, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A transmission device comprising: a firstdetection unit that detects a signal which is outputted from a displaydevice to the transmission device, wherein the signal is used fordetermining whether an acquisition of information relating to thedisplay device is allowed, wherein the information is used for detectinga capability of the display device; an acquiring unit that acquires theinformation from the display device after the acquisition of theinformation is allowed; a transmission unit that transmits image data,generated using the information acquired from the display device, to thedisplay device via a transmission line; a second detection unit thatdetects whether the transmission line and a terminal resistor of thedisplay device are connected; and a control unit that controls, based ona status of the signal detected by the first detection unit and adetection result of the second detection unit, whether the transmissionunit transmits image data, generated using the information, to thedisplay device via the transmission line, wherein the control unitcauses the transmission unit not to transmit image data, generated usingthe information, to the display device via the transmission line if theacquisition of the information is allowed and the transmission line isnot connected to the terminal resistor of the display device.
 2. Thetransmission device according to claim 1, wherein the informationincludes at least one of Enhanced Extended display identification data(E-EDID) and Extended display identification data (EDID).
 3. A methodcomprising: detecting a signal which is outputted from a display device,wherein the signal is used for determining whether an acquisition ofinformation relating to the display device is allowed, wherein theinformation is used for detecting a capability of the display device;acquiring the information from the display device after the acquisitionof the information is allowed; detecting whether a transmission line anda terminal resistor of the display device are connected, wherein thetransmission line is used for transmitting image data, generated usingthe information acquired from the display device, to the display device;controlling, based on a status of the detected signal and a detectionresult of whether the transmission line and the terminal resistor of thedisplay device are connected, a transmission of image data generatedusing the information; and causing not to transmit image data, generatedusing the information, to the display device via the transmission lineif the acquisition of the information is allowed and the transmissionline is not connected to the terminal resistor of the display device. 4.The transmission device according to claim 1, wherein the control unitcauses the transmission unit to transmit image data, generated using theinformation, to the display device via the transmission line after thetransmission line and the terminal resistor of the display device areconnected if the acquisition of the information is allowed.
 5. Atransmission device comprising: a first detection unit that detects asignal which is outputted from a display device to the transmissiondevice, wherein the signal is used for determining whether anacquisition of information relating to the display device is allowed,wherein the information is used for detecting a capability of thedisplay device; an acquiring unit that acquires the information from thedisplay device after the acquisition of the information is allowed; atransmission unit that transmits image data, generated using theinformation acquired from the display device, to the display device; asecond detection unit that detects whether the display device is in afirst state, wherein the first state is a state where the display deviceis in a power on state and a state where image data to be transmittedfrom the transmission unit to the display device is selected as imagedata to be displayed by the display device; and a control unit thatcontrols, based on a status of the signal detected by the firstdetection unit and a detection result of the second detection unit,whether the transmission unit transmits image data, generated using theinformation, to the display device, wherein the control unit causes thetransmission unit not to transmit image data, generated using theinformation, to the display device if the acquisition of the informationis allowed and the display device is in a second state, and wherein thesecond state is different from the first state.
 6. The transmissiondevice according to claim 5, wherein the information includes at leastone of Enhanced Extended display identification data (E-EDID) andExtended display identification data (EDID).
 7. The transmission deviceaccording to claim 5, wherein the control unit causes the transmissionunit to transmit image data, generated using the information, to thedisplay device after a state of the display device is changed from thesecond state to the first state if the acquisition of the information isallowed.
 8. A method comprising: detecting a signal which is outputtedfrom a display device, wherein the signal is used for determiningwhether an acquisition of information relating to the display device isallowed, and wherein the information is used for detecting a capabilityof the display device; acquiring the information from the display deviceafter the acquisition of the information is allowed; detecting whetherthe display device is in a first state, wherein the first state is astate where the display device is in a power on state and a state whereimage data to be transmitted to the display device is selected as imagedata to be displayed by the display device; controlling, based on astatus of the detected signal and a detection result of whether thedisplay device is in the first state, a transmission of image data,generated using the information, to the display device; and causing notto transmit image data, generated using the information, to the displaydevice if the acquisition of the information is allowed and the displaydevice is in a second state, wherein the second state is different fromthe first state.
 9. The transmission device according to claim 1,wherein the information includes information relating to a color spacesupported by the display device, and wherein the information includesinformation relating to a resolution supported by the display device.10. The transmission device according to claim 1, wherein theinformation includes information relating to a video format supported bythe display device, and wherein the information includes informationrelating to an audio format supported by the display device.
 11. Thetransmission device according to claim 5, wherein the informationincludes information relating to a color space supported by the displaydevice, and wherein the information includes information relating to aresolution supported by the display device.
 12. The transmission deviceaccording to claim 5, wherein the information includes informationrelating to a video format supported by the display device, and whereinthe information includes information relating to an audio formatsupported by the display device.
 13. The method according to claim 3,wherein the information includes at least one of Enhanced Extendeddisplay identification data (E-EDID) and Extended display identificationdata (EDID).
 14. The method according to claim 3, further comprisingcausing to transmit image data, generated using the information, to thedisplay device via the transmission line after the transmission line andthe terminal resistor of the display device are connected if theacquisition of the information is allowed.
 15. The method according toclaim 3, wherein the information includes information relating to acolor space supported by the display device, and wherein the informationincludes information relating to a resolution supported by the displaydevice.
 16. The method according to claim 3, wherein the informationincludes information relating to a video format supported by the displaydevice, and wherein the information includes information relating to anaudio format supported by the display device.
 17. The method accordingto claim 8, wherein the information includes at least one of EnhancedExtended display identification data (E-EDID) and Extended displayidentification data (EDID).
 18. The method according to claim 8, furthercomprising causing to transmit image data, generated using theinformation, to the display device after a state of the display deviceis changed from the second state to the first state if the acquisitionof the information is allowed.
 19. The method according to claim 8,wherein the information includes information relating to a color spacesupported by the display device, and wherein the information includesinformation relating to a resolution supported by the display device.20. The method according to claim 8, wherein the information includesinformation relating to a video format supported by the display device,and wherein the information includes information relating to an audioformat supported by the display device.
 21. A transmission devicecomprising: a first detection unit that detects a signal which isoutputted from a display device to the transmission device, wherein thesignal is used for determining whether an acquisition of informationrelating to the display device is allowed, wherein the information isused for detecting a capability of the display device; an acquiring unitthat acquires the information from the display device after theacquisition of the information is allowed; a transmission unit thattransmits image data, generated using the information acquired from thedisplay device, to the display device via a transmission line; a seconddetection unit that detects whether the transmission line and a terminalresistor of the display device are connected; and a control unit thatcontrols, based on a status of the signal detected by the firstdetection unit and a detection result of the second detection unit,whether the transmission unit transmits image data, generated using theinformation, to the display device via the transmission line after atransmission of image data, generated using the information, to thedisplay device via the transmission line is started, wherein the controlunit causes the transmission unit not to transmit image data, generatedusing the information, to the display device via the transmission lineif the acquisition of the information is allowed and the transmissionline is connected to the terminal resistor of the display device, afterthe transmission of image data, generated using the information, to thedisplay device via the transmission line is started.
 22. Thetransmission device according to claim 21, wherein the informationincludes at least one of Enhanced Extended display identification data(E-EDID) and Extended display identification data (EDID).
 23. Thetransmission device according to claim 21, wherein the informationincludes information relating to a color space supported by the displaydevice, and wherein the information includes information relating to aresolution supported by the display device.
 24. The transmission deviceaccording to claim 21, wherein the information includes informationrelating to a video format supported by the display device, and whereinthe information includes information relating to an audio formatsupported by the display device.
 25. A method comprising: detecting asignal which is outputted from a display device, wherein the signal isused for determining whether an acquisition of information relating tothe display device is allowed, wherein the information is used fordetecting a capability of the display device; acquiring the informationfrom the display device after the acquisition of the information isallowed; detecting whether a transmission line and a terminal resistorof the display device are connected, wherein the transmission line isused for transmitting image data, generated using the informationacquired from the display device, to the display device; controlling,based on a status of the detected signal and a detection result ofwhether the transmission line and the terminal resistor of the displaydevice are connected, a transmission of image data generated using theinformation, after a transmission of image data, generated using theinformation, to the display device via the transmission line is started;and causing not to transmit image data, generated using the information,to the display device via the transmission line if the acquisition ofthe information is allowed and the transmission line is not connected tothe terminal resistor of the display device, after the transmission ofimage data, generated using the information, to the display device viathe transmission line is started.
 26. The method according to claim 25,wherein the information includes at least one of Enhanced Extendeddisplay identification data (E-EDID) and Extended display identificationdata (EDID).
 27. The method according to claim 25, wherein theinformation includes information relating to a color space supported bythe display device, and wherein the information includes informationrelating to a resolution supported by the display device.
 28. The methodaccording to claim 25, wherein the information includes informationrelating to a video format supported by the display device, and whereinthe information includes information relating to an audio formatsupported by the display device.
 29. A transmission device comprising: afirst detection unit that detects a signal which is outputted from adisplay device to the transmission device, wherein the signal is usedfor determining whether an acquisition of information relating to thedisplay device is allowed, wherein the information is used for detectinga capability of the display device; an acquiring unit that acquires theinformation from the display device after the acquisition of theinformation is allowed; a transmission unit that transmits image data,generated using the information acquired from the display device, to thedisplay device; a second detection unit that detects whether the displaydevice is in a first state, wherein the first state is a state where thedisplay device is in a power on state and a state where image data to betransmitted from the transmission unit to the display device is selectedas image data to be displayed by the display device; and a control unitthat controls, based on a status of the signal detected by the firstdetection unit and a detection result of the second detection unit,whether the transmission unit transmits image data, generated using theinformation, to the display device after a transmission of image data,generated using the information, to the display device, wherein thecontrol unit causes the transmission unit not to transmit image data,generated using the information, to the display device if theacquisition of the information is allowed and the display device is in asecond state, after the transmission of image data, generated using theinformation, to the display device, is started, and wherein the secondstate is different from the first state.
 30. The transmission deviceaccording to claim 29, wherein the information includes at least one ofEnhanced Extended display identification data (E-EDID) and Extendeddisplay identification data (EDID).
 31. The transmission deviceaccording to claim 29, wherein the information includes informationrelating to a color space supported by the display device, and whereinthe information includes information relating to a resolution supportedby the display device.
 32. The transmission device according to claim29, wherein the information includes information relating to a videoformat supported by the display device, and wherein the informationincludes information relating to an audio format supported by thedisplay device.
 33. A method comprising: detecting a signal which isoutputted from a display device, wherein the signal is used fordetermining whether an acquisition of information relating to thedisplay device is allowed, and wherein the information is used fordetecting a capability of the display device; acquiring the informationfrom the display device after the acquisition of the information isallowed; detecting whether the display device is in a first state,wherein the first state is a state where the display device is in apower on state and a state where image data to be transmitted to thedisplay device is selected as image data to be displayed by the displaydevice; controlling, based on a status of the detected signal and adetection result of whether the display device is in the first state, atransmission of image data, generated using the information, to thedisplay device after a transmission of image data, generated using theinformation, to the display device; and causing not to transmit imagedata, generated using the information, to the display device if theacquisition of the information is allowed and the display device is in asecond state after the transmission of image data, generated using theinformation, to the display device, wherein the second state isdifferent from the first state.
 34. The method according to claim 33,wherein the information includes at least one of Enhanced Extendeddisplay identification data (E-EDID) and Extended display identificationdata (EDID).
 35. The method according to claim 33, wherein theinformation includes information relating to a color space supported bythe display device, and wherein the information includes informationrelating to a resolution supported by the display device.
 36. The methodaccording to claim 33, wherein the information includes informationrelating to a video format supported by the display device, and whereinthe information includes information relating to an audio formatsupported by the display device.